1. Field of the Invention
This invention pertains to a concrete compaction system.
2. Description of the Related Art
The purpose of a system of this type is to compact concrete while it is still plastically deformable after it has been filled into a form for the production of concrete parts. There are at least one, and commonly more vibration units fastened to the forms that frequently each have an external vibrator. This type of external vibrator commonly consists of a motor that drives one or more eccentric elements consisting of centrifugal weights, thus producing an oscillation that is transferred to the forms by means of a fixed connection. By vibrating the forms, the concrete can be compacted in the desired fashion.
Commonly, a number of external vibrators are arranged at the forms for larger concrete parts. All of these vibrators are coupled to a common frequency converter that provides an electrical AC current at the desired frequency for the electric motors that are connected together.
In practice, the problem frequently arises that certain areas of the forms and thus certain parts of the concrete are not sufficiently vibrated and thus not compacted. When the user has recognized this problem he commonly raises the frequency provided by the frequency converter. However, the increase in frequency affects all connected external vibrators at the same time, independent of whether the vibrators are located near the weakly agitated concrete or at a position with already strong agitation. This results in a considerable amount of noise and loading of material, which is disadvantageous both for the user as well as for the forms.
From DE 195 42 868 A1, a concrete compaction system is known with two vibration units fastened to one form, each having one oscillator.
Acceleration sensors fastened to the vibration units detect the oscillation of each form and the signal detected is forwarded to a common signal-processing unit. At the signal-processing unit, a subsequent data-processing logic algorithm issues a prognosis on the product quality to be expected of the concrete form parts from the measured values and from stored comparison values.
The central controller that governs all vibration units requires a very exact determination of the parameters possible during operation in advance. To this end, it is suggested that, for example, an expert catalog be stored in memory. Thus, the adjustment of the compaction system for various form parts and in operating more than two vibration units requires a very considerable amount of work to establish the expert catalog.
A similar system is known from DE 297 12 242 U1. Here, a number of oscillators are provided at a vibrator table. The frequency of the oscillators and relative phase position are individually adjustable. In addition, a number of sensors are located at the vibrator table that detect the overall reaction, i.e. the overall oscillation of the vibrator table and send this as a measured signal to a common controller. In this system, it is also required that expensive regulatory algorithms, characteristic fields, etc. be stored in memory in the vector regulators acting as the controller in order to obtain the desired complex oscillation reactions. Otherwise, the information from the sensors cannot be satisfactorily evaluated.
A basically similar design is given in DE 36 40 079 A1.
The objective of the invention is to provide a concrete compaction system in which only those areas of the forms not oscillating with the desired intensity are agitated stronger, wherein a flexible and simple adjustment of the concrete compaction system to various form geometries and a varying numbers of external vibrator is the goal.
According to the invention, the objective is met by means of a concrete compaction system with the features recited in the claims. Advantageous developments of the invention are found in the dependent claims.
According to the invention, a number of vibration units are provided that each has its own oscillator, its own acceleration sensor, its own frequency converter and its own controller. In this way, the intensity of the oscillation at the individual points of the form can be very exactly and individually adjusted by controlling the individual vibration units. In order to enable a coordination of the controls, in an advantageous development the controls of each of the vibration units are coupled through a data line to one another. The data line can also be connected to a common control processor that serves to individually control the vibration units.
The solution according to the invention makes it possible to detect, through the acceleration sensor, the oscillations acting on the form. A constantly changing acceleration value corresponding to the oscillation is sent to the controller, which can vary the operating parameters of the oscillator accordingly in order to produce the desired oscillation at the form. Thus, for example, it is possible that the controller raises the frequency of the oscillator if the acceleration sensor has detected an oscillation of the form that is too low.
By adjusting the frequency converter through the controller, it is possible to vary the oscillation frequency of the oscillator in a simple manner.
In an especially advantageous embodiment form of the invention, the acceleration sensor is fastened to the oscillator or to the form. In this way, it is possible that the acceleration sensor can either sense the oscillation directly at the form orxe2x80x94due to the oscillator being rigidly fixed to the formxe2x80x94at the oscillator that experiences the same oscillation.
The target values for the individual controls provided at the vibration units can be the frequency of the oscillator, a target acceleration or an allowable control range within which the individual controls can adjust the oscillator depending on the measured oscillation signal.